Control apparatus



Feb. 9, 1960 F. T. DEZIEL CONTROL APPARATUS Filed Nov. 27, 1957 N "8 InN LINE SWITCH com 3 Sheets-Sheet 1 INVENTOR.

FRED T. DEZIEL j Md/Jw A TTOR/VE Y Feb. 9, 1960 F. T. DEZJEL CONTROLAPPARATUS 3 Sheets-Sheet 2 Filed NOV. 27, 1957 INVENTOR,

I FRED T DEZIEL ATTORNEY Feb. 9, 1960 F. 'r. DEZlEL 2,924,270

CONTROL APPARATUS Filed Nov. 27, 1957 3 Sheets-Sheet 3 LINE SWITCHCONTROLLER 18 GEIGER TUBE 'INVENTOR. FRED I DEZIEL ATTORNEY tectionportion thereof.

United States Patent CONTROL APPARATUS Fred T. Deziel, Bloomington,Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn, a corporation of Delaware Application November 27, 1957 Serial No.699,235

Claims. (Cl. 158-125) This invention is concerned with an improvedcontrol apparatus and particularly with a control apparatus utilizing aGeiger tube type condition sensor in conjunction with a quenchingcircuit and a safe-start relay.

As is well known, a Geiger tube may be used to sense the presence ofvarious conditions. For example, flame at a fuel burner unit. The Geigertube may be either of the self-quenching type or of thenon-selfquenching type. If of the non-selfquenching type, it isnecessary to provide a quenching circuit, with the Geiger tube and thequenching circuit interconnected in mutual controlling relationship suchthat upon the Geiger tube being ionized, a signal is fed to thequenching circuit, and the quenching circuit in turn quenches, ordionizes, the Geiger tube.

This quenching circuit utilizes a hot cathode type discharge device andupon the initial application of voltage to the apparatus it is desirableto provide a means to delay the application of operating voltage to theGeiger tube until the hot cathode discharge device becomes heated to itsoperating temperature, to thereby be in a condition to quench the Geigertube. Such a construction prevents sustained discharge through theGeiger tube during the Warmup period of the quenching circuit andthereby prevents a period of instability of the Geiger tube. Thisfeature of providing means to delay the application of operating voltageto the Geiger tube is shown in the copending application of Robert O.Engh, Serial No. 646,- 125, filed March 14, 1957.

Such a Geiger tube and associated circuitry can be utilized with aburner control apparatus as the flame de- It then becomes desirable, oninitial call for operation of the burner, to check the operation of theflame detector before allowing the fuel to be admitted to the fire box.This is accomplished by providing a safe-start relay which initiallysimulates the presence of flame, with the apparatus includinginterlocking circuit means which insures that the main burner controlrelay is not energized unless the flame detector responds to thesimulated presence of flame.

Such a construction is particularly advisable in the case of anelectronic flame detector which utilizes hot cathode type dischargedevices. this construction can be seen by assuming that a power failureshould occur. The discharge devices of the electric flame detector thencool and the flame detector assumes a non-flame condition. Upon thesubsequent restoration of power to the apparatus, the flame detectorremains in the non-flame condition since the discharge devices have notas yet heated to operating temperature. There is no assurance, however,that a fault does not exist in the flame detector which willsubsequently cause the flame detector to assume a flame condition,independent of the actual presence of flame, once the discharge devicesare heated. If such a fault does in fact exist, the flame detectorassumes a flame condition when the discharge devices are heated, thusindicating the pilot flame has again been reestablished at the fuelburner The advisability of 2,924,270 Patented Feb. 9, 1960 2 unit. Themain valve then opens and if the pilot flame has not been established,unburned fuel floods the fire box.

By providing the safe start relay, which relayfirst simulates a flameand upon the flame detector responding to the simulated presence offlame then removes the simulated flame to cause the flame detector toassume a flame and then no-flame condition, and furthermore providingmeans to insure that the apparatus must go through this sequence beforethe main valve can be energized, the proper operation of the flamedetector is checked and if such a fault does exist, the main valve isnot energized.

The present invention is directed to an arrangement whereby the safestart relay, as above mentioned, not only checks the operation. of theflame detector but also prevents application of operating voltage to theGeiger tube until the quenching circuit is in a condition to quench theGeiger tube. As above mentioned, this prevents a sustained discharge tothe Geiger tube during a warmup period of the quenching circuit andthereby eliminates a period of instability of the Geiger tube.

While the modifications of this invention are shown in conjunction withthe flame sensor, it will be readily understood that the presentinvention can be equally applied to the sensing of any condition towhicha Geiger tube is sensitive.

It is therefore an object of the present invention to provide animproved condition responsive control apparatus utilizing a Geiger tubeand a quenching circuit therefor and utilizing a safe start relay, withthe Geiger tube, quenching circuit and safe start relay interconnectedto provide for a delay of the application of operating voltage to theGeiger tubeand to first provide for a simulated presence of a conditionto cause the safe start relay to be operated, and second to cause anoperating voltage to be applied to the Geiger tube and remove thesimulated presence of the condition.

Other objects of the present invention will be apparent to those skilledin the art upon reference to the following speciflcation, claims anddrawings, of which Figure 1 is a schematic showing of the presentinvention associated with a fuel burner unit, disclosing a burnercontrol apparatus utilizing the present invention,

Figure 2 is a modification of a portion of the apparatus, wherein onlythe Geiger tube, the quenching circuit and the safe start relay havebeen shown for purposes of simplicity, and

Figure 3 is a showing of a further modification of the presentinvention.

Referring specifically to Figure 1, the reference numeral 1t designatesa fuel burner unit having a main burner 11, a pilot burner 12, a mainvalve 13, a pilot valve 14, and ignition means 15.

Reference numeral 16 designates a Geiger tube having a cathode .17 andan anode 18. This Geiger tube is positioned to be subjected to the flameat the fuel burner unit and upon being subjected to a flame, the Geigertube ionizes to pass a current to an electronic network includingelectron discharge devices 19 and 25. The discharge device 19 is a gasfilled type of discharge device and includes an anode 20, a controlelectrode 21, a cathode 22 and a further electrode 23. This dischargedevice is a portion of the quenching circuit for the Geiger tube 16 andthe cathode of this discharge device must filed June 21, 1956. Thisinterconnection issuch that the signal voltage applied to the controlelectrode 29is applied directly from the quenching'circuit whereasthesignal voltage applied to the control electrode 30 is integrated bymeans of the network including capacitor 31 and resistor 32.

The discharge devices 19 and 25, as well as the Geiger tube 16, receivetheir operating voltage from a transformer 33 having a primary winding34'and secondary windings 35 and 36. The output of the flame detectorincludes a flame relay 37 having an actuating winding 38 and switches39, 40 and 41. The switches 39 and 40 are normally open switches and theswitch 41 is a normally closed switch. Upon energization of thewinding38, switches 39 and 40 close whereas switch 41 opens. l

The flame relay 37 cooperates with a further relay 42, which can bedesignated the safe start relay. This relay includes an actuatingwinding 43 and normally open switches 44 and 45 as well as the normallyclosed switch 46. Upon energization of the winding 43, the switches 44and 45 assume a closed condition whereas the switch 46 assumes an opencondition. a

The reference numeral 47 designates a main burner control relay havingan actuating winding 48 and normally open switches 49 and 50 as well asthe normally closed switch 51. Upon energization of the winding 48, theswitches 49 and 50 assume a closed position and the switch 51 assumes anopen position.

The reference numeral 52' designates a safety cutout means in the formof a bimetal operated safety switch. This safety switch is provided withan actuating heater 53 which heats bimetal 54. Bimetal 54, when hot,warps to the left and causes the switch 55 to open, as shown by thearrow labeled H. Upon subsequent cooling of the bimetal, the resetbutton 56 may be depressed toreset the safety switch 52 to the conditionshown in Figure l.

The control apparatus shown in Figure '1 includes power input terminals57 and 58 which are'adapted to be connected to a source of alternatingvoltage, not shown. This source of voltage supplies energizing voltageto the components of the control apparatus as well as to the fuel burnerunit and is controlled by a line switch 59 and a controller 60. Thiscontroller 60 may be a manual controller or an automatic controllerresponsive to a condition such as temperature which is in turn.controlled by operation of the fuel burner unit 10. Referring nowspecifically to the operation of the flame detector including Geigertube 16 and discharge devices 19 and 25. As above mentioned, operatingvoltage is derived from transformer 33, and specifically the secondarywindings 35 and 36 thereof. Winding 35 is provided with a rectifier 61and a capacitor 62 which consists of a source of direct current voltagehaving the polarity indicated on capacitor 62. This winding is'providedwith a tap which is connected to a further capacitor 63 and a furtherrectifier '64 and then to the lower end terminal of the secondarywinding 35. This circuit provides a source of biasing voltage, of thepolarity shown on capacitor 63, which tends, to bias discharge device 25substantially to cutoff. The cathode 27 of this discharge deviceisconnected to the positive plate of capacitor 63 and the negative plateof this capacitor is connected through resistor 65 to controlelectrode29 and through resistor 66 to control electrode 30. The

anode of this discharge device 25 isconnected through the winding 38 ofthe flame relay 37 to the positive terminal of capacitor 62, therebyapplying apositiveoperating voltage to the anodeof this dischargedevice,

tor 62 and the cathode of this discharge device is connected through anetwork including resistors 68, 66, 65, and 32 and capacitor 31, andfurther through rectifier 64 to the negative plate of this capacitor 62,thereby applying an operating voltage, to the anode and cathode ofdischarge device 19.

Upon discharge device 19 being rendered conductive, capacitor 72discharges through resistor 67 and the anode and .cathode of dischargedevice 19 and back to the negative plate of capacitor 72. Upon dischargeof capacitor 72, capacitor 62 begins to recharge capacitor 72,

with current flowing from the positive plate of capacitor 62 tocapacitor 72. At this point the current divides into two paths. Thefirst path consists of the series connected resistors 68 and 65. Thesecond path consists,

of resistor 32 connected in series with the parallel connected resistor66 and capacitor 31., The, current flow circuit is then completed tiveplate of capacitor 62. p v

It willbe recognizedthat in the above traced circuit the first branchconsistingof resistor 68 and resistor 65 applies a positive voltage tothe control electrode 29 of discharge 25, this voltage being directlyapplied to this control electrode. However, the positive voltage appliedto the control electrode 30 is integrated by means of the networkincluding capacitor 31 and therefore this voltage is delayed orintegrated with respect to the voltage applied to control electrode 29.As explained in the above mentioned co-pending Fred T. Dezielapplication,

this discriminates against or eliminates the efi'ect of the inherentbackground count of the Geiger 'tube 16.

Geiger tube 16 and discharge device 19 are connected 1 in mutualcontrolling relationship, this relationship being through a resistor 67to the positive plate of the capacii Assume for the moment that safe theenergized position to thereby open the switch 46 and 1 controlled by theswitchmeans of safe start relay 42. The cathode 17 of Geiger tube 16isconnected directly to the control electrode 21 of discharge device119. The 1 anode 18 of this Geigertnbe is connected to the normally openswitch 45 of safe start relay 42. Therefore, with relay 42 de-energizedthe Geiger tube 16 is not connected in controlling relation to dischargedevice '19 nor is an Operating voltage applied to the Geiger tube. Withrelay 42 de-energized, the control electrode 21 of discharge device 19is connectedto theanode 20 through a resistor 69 and through thenormally closed switch 46 of relay 42. This connection simulates thepresence of flame at the fuel burner unit 10 and causesdischargedevice19" to be conductive, for -the reasons to be described.

A biasing means for dischargedevice 19 is provided from-the secondaryWinding 36 of'transformer 33 in combination with a rectifier 70 and acapacitor 71. This circuit provides for biasing discharge device 19substantially to cutoif. Winding 36 also energizes heater 24 of,discharge devic 19. 9 l

start relay 42 is in toclose-the switch 45. Further assume that there isno flame present at the fuel burner, unit 10. In this condition thedischarge devices-19 and 25 are non-conductive due to the cutoif biassupplied to the control electrodes thereof. The Geiger tube 16 has anoperating voltage applied thereto and is in a condition to sense ,aflame at the burner unit 10. Ha flame is now established at the burnerunit 10, the Geiger tube 16 ionizes to pass currentthrough a circuitwhich can be traced from, the t positive plate of capacitor 172 throughresistor.67,. conductor 72, switch 45, conductor 73, Geiger tube116,conductor 7 4,"resistor 75, rectifier 70, transformer winding 36 andconductors 76 and 77, back to the negative plate of capacitor 172. Atthis point the current path splits into two branches; The first branchincludesthe series connected resistors 68 and 65. The second branchincludes resistor32 connected in serieswiththe parallel connectedresistor 66 and capacitor 31. The charging 1 current flow circuit thencontinues through rectifier 64 to the lower plate of capacitor 62. Itcan be seen from 1 through rectifier 64 to the negaw this current flowpath that a voltage is developed across resistor 75 which opposes thecutofi voltage developed across capacitor 71 and thereby causesdischarge device 19 to become conductive. Discharge device 19 is a highcurrent conducting device, relative to the current which is conductiveby Geiger tube 16, this device now becomes conductive and dischargescapacitor 172 which is effective to substantially drop the voltageacross the electrodes of Geiger tube 16 and to thereby quench this tube.This discharge circuit for capacitor 172 has been previously traced andit can be seen from this circuit that a voltage is also developed acrossthe resistors 65 and 68 as well as the resistors 32 and 66, resistor 66being shunted by capacitor 31.

The Geiger tube 16 has now been quenched as above described and thevoltage developed across resistor 75 which initiated discharge of device19 is now no longer present.

A short time period must elapse to recharge capacitor 172 before thisoperating voltage is applied to the Geiger tube and to discharge device19. This recharging circuit, as has been described, can be traced fromthe positive plate of capacitor 62 through capacitor 172. At this pointthe current branches into two circuits. The first circuit includesseries connected resistors 68 and 65. The second circuit includesresistor 32 connected in series with parallel connected resistor 66 andcapacitor 31; The recharging time of capacitor 172 determines thefrequency or repetition rate at which the Geiger tube 16 is allowed tosense a flame at the fuel burner unit 10.

Upon capacitor 172 once being charged such that an operating voltage isapplied through the Geiger tube, the Geiger tube again ionizes, due tothe presence of fire at the fuel burner unit 10, and the above sequenceof operation again takes place to once again apply a signal voltage tothe network including resistors 32, 65, 66 and 68 and capacitor 31.After a suflicient number of these signal voltages pulses have beenapplied to the integrating capacitor 31, this capacitor charges suchthat a voltage appears on both of the control electrodes 29 and 30 atthe same time and at this time the discharge device 25 becomesconductive to energize the winding 38 of the flame relay 37.

Turning now to the explanation of the complete control apparatus, theapparatus in Figure 1 is shown in a condition wherein alternatingvoltage is not applied to the power input terminals 57 and 58. If it isassumed that a voltage is now applied to these terminals and that lineswitch 59 is closed, the primary winding 34 of transformer 33 isenergized through a circuit which can be traced from terminal 57 throughline switch 59, conductors 78, 79 and 80, transformer primary winding34, conductor 81, safety switch 52, and conductor 82 to the terminal 58.This connection energizes secondary windings 35 and 36 and operatingvoltages are applied to the .dis-

charge devices 19 and 25. Due to the fact that the safe start relay 42is de-energized at this time, an operating voltage is not applied to theGeiger tube 16. As above explained, with relay 42 deenergized thecontrol electrode 21 of discharge device 19 is connected throughresistor 69 and through the switch 46 to the anode of this dischargedevice. After an initial time delay during which the cathode ofdischarge device 19 is heating, discharge device 19 becomes conductiveand a voltage is developed on control electrodes 29 and 30 of dischargedevice 25 to cause this discharge device to in turn become conductive.This energizes the winding 38 of flame relay 37 to cause the switch 40of this relay to close.

When this switch 48 closes, an energizing circuit is completed for thewinding 43 of the safe start relay 42. This energizing circuit can betraced from the terminal 57 through line switch 59, conductors 78, 79and 83, winding 43, conductor 84, heater 53, conductors 85 and 86,switch 51 of the main burner control 'relay' 47, conductor 87, switch 48of flame relay 37, conductors 88 6 and 81, safety switch 52, andconductor 82 to the terminal 58. g

This above traced circuit energizing the. winding of safe start relay43. It will be noted from the above traced circuit that in order for thewinding of safe start relay 42 to be energized at this time it isnecessary that main burner control relay 47 to be de-energized and thatthe flame relay 37 be energized. In this manner, the operation of theflame detector is checked since the flame is simulated and the flamedetector has responded to this simulated presence of flame to energizethe flame relay 37. Furthermore, in order for the flame detector torespondto this simulated presence of flame it is necessary that thedischarge device 19 be operative. Therefore, the energization of flamerelay 37 is indicative of the fact that the quenching circuit, includingdischarge device 19, is now in an operating condition. Therefore,although operating voltage is not at this time applied to the Geigertube 16, the apparatus has checked to insure that the quenching circuitis operative before allowing the safe start relay 42 to be energized.Furthermore, it is impossible at this time for the controller toenergize the main burner control relay 47 since the energizing circuitfor this relay is broken at the switch 41 of the flame relay 37. Thisinsures that the main burner control relay 47 may not be energizedduring the checking period 'of the apparatus.

Energization of the safe start relay 42 ends simulated presence of flameby the opening of switch 46. The closing of switch 45 places the Geigertube 16 in controlling relationship to the discharge device 19 andplaces an operating voltage on the Geiger tube. It will be rememberedthat there is no flame present at the fuel burner unit at this time andtherefore the Geiger tube 16 normally will not become energized.

However, the Geiger tube does have an inherent background count which iscaused by ionizing events passing through the Geiger tube from randomsources of radiation. In the event that Geiger tube 16 does becomeionized by one of these random ionizing events, the quenching circuitincluding the discharge device 19 is now effective to quench the Geigertube. Furthermore, the means by which the voltage applied to the controlelectrode 30 of discharge device 25 is integrated with respect to thevoltage applied to the control electrode 29 insures that the flame relay37 will not respond to this random ionizing event.

Energization of the safe start relay 42 likewise causes the switch 44 toassume a closed condition to thereby complete a holding energizingcircuit for the winding 43 of this relay. This holding energizingcircuit can be traced from the terminal 57 through the line switch 59,conductors 78, 79 and 83, winding 43, conductor 89, switch 44,

conductor 90, the lower portion of the primary winding 34, conductor 81,safety switch 52 and conductor 82 to the terminal'58. This above tracedcircuit insures that the winding 43 of the safe start relay will remainenergized so long as voltage is continuously supplied to, the terminals57 and 58. However, in the case of a power failure, the winding 43 willbe de-e'nergi'zed as well as the other components of the controlapparatus. Upon the re-establishment of voltage at the terminals 57 and58,

it is necessary for the control apparatus to again go through a checkingsequence where flame is simulated and the flame relay 37 is energized inresponse to this simulated flame, as above described.

As above described, when the safe start relay 42 is energized, switch 46opens to thereby end the simulation of flame. The flame detector mustnow respond to the absence of flame at the burner unit 10 to'de-energize the flame relay 37. When the flame detector does sorespond, switch 40 of time relay 37 again opens to thereby break theinitial energizing circuit of the safe start relay 42 and to closeswitch 41 which is in the initial energizing circuit of the main burnercontrol relay 48. The appa- 7 ratus is now in the standby conditionwherein controller 60 is in the condition to control ,the operation, ofthe fuel burner unit 10. i i

Assume now that the controller 60 closes, an energizing circuit is nowcompleted for the winding 48 of the main burner control relay 47.. Thisenergizingcircuit canbe traced from terminal 57 through line switch 59,controller 60, winding 48, conductor 91, switch 41 of flame relayf37,conductor 85, heater 53, conductors 84 and 89, switch 44 of safe startrelay 42, conductor 90, the lower portion of transformer primary winding34, conductor 81, safety switch 52, and conductor 82 to the terminal 58.It can be seen from this above tracedcircuit that the winding 48 of the,main burner 'control relay is not energized unless the flame relay 37 isin its de-energized condition indicating the absence of flame and thesafe start relay 42 is inthe energized condition indicating that theelectronic flame detector has'responded to the simulated presence offlame. and the subsequent absence of flame, thereby indicating that theflame detector is operating properly.

Energization of winding 48 of the main burner control relay causes theswitch 49 of this relay to close. This completes a holding energizingcircuit for the winding 48 of this relay and this circuit can be tracedfrom the terminal 57 through line switch 59, controller 60, winding 48,switch 49, conductor 92, safety switch 52, and

conductor 82 to the terminal 58.

Energizing of relay 47 also causes the switchSl to open. It will beremembered that this switch is in the initial energizing circuit of thesafe start relay 42 and therefore the opening of this switch maintainsthe initial energizing circuit of this relay open even though the flamerelay 37 may subsequently be energized, as it will be when the flame isdetected in the fuel burner unit. 10. Energizing of the main burnercontrol relay. 47 also causes the switch 50 to close and therebycompletes an energizing circuit for the ignition means 15 and the pilotvalve 14 of the fuel burner unit .10. This energizing circuit can betraced from the power line terminal 57 through line switch 59,conductor-78, switch50, and conductor 93 to the ignition means 15 andthe pilotvalve 14. The circuit is completed through conductors 94 and95, safety switch 52 and conductor 82 to the power line terminal 58. Y

A flame is normally now established at the pilot burner 12 and thisflame is sensed by the Geiger tube 16. As above described, Geiger tube16 becomes ionized and causes discharge device 19 to become conductive.The conduction of discharge device 19 subsequently quenches the Geigertube and as a result the Geiger tube' 16 and the discharge device 19cycle'between states of conduction and non-conduction to produce asignal voltage on the control electrodes 29 and 30 of the dischargedevice 81 and 92, switch 49 of relay 47, conductor 91, switch 41 ofrelay 37, conductor 85, heater 53, conductors 84and 89, switch 44 ofrelay 42, and conductor 90 to the tap provided on the primary winding oftransformer33 This above traced circuit provides for a pilot flame proving period which may extend anywhere from 15 to 90seconds' dependingupon the construction of the safety switch 52. In the event that a pilotflame is not established within this time period, the bimetal 54 warpsto the left and opens the switch 55 to thereby disconnect the. apparatusfrom .thepower line terminal 58. Normally however a flame is establishedwithin this period, to energize flame relay 37.

. Energization of flame relay .37 opens the switch pleted through switch39, conductors 96 and; 95, safety switch 52, and conductor 82 to thepower line terminal I The apparatusiof Figure l is now in its runningcondition wherein a flame is present at the burners 11 and 12 and theGeiger tube 16 continuously senses the flame. In the event that there isa subsequent flame failure, the Geiger tube senses the absence of flameand the flame relay 37 becomes de-energized. This causes switch39to'open to thereby de-energize the main fuel valve 13 and furthermorecloses the switchn41 to again energize the heater 53 of safety switch52. After a given time period, for example 15 to seconds, the safetyswitch 52 is operative to open and to de-energize the entir apparatus. e

Normally however a flame continues at the burners 11 and 12 until thecontroller. 60 opens. Upon opening of this controller, themain-burnercontrol relay 47 is de-energized to open the switch 50 and therebydeenergize all the components of the fuel burner unit 10. Furthermore,the switch 51 closes to complete a component checking circuit which onceagain energizes the heater 53 ofthe safety switch. This circuit canbetraccd from the lower terminal of the primary winding 34 throughconductor 88, switch 40, conductor 87, switch 51, conductors 86 and'85,heater 53, conductors 84 and 89, and switch 44 and conductor 90 to thetap of primary winding 34. This circuit checks the flame detector sincethe safety switch 52 is effective to'allow the electronicflame detector,including the Geiger tube 16, from 15 to 90 seconds to sense the absenceof flameat the 42 functions to not only check the proper operation I ofthe flame detector but also prevents the application of operatingvoltage to the Geiger tube 16 until the quenching circuitincluding thedischarge device 19 is in a condition where itis operative to quench theGeiger tube.

Figure 2 shows a modificationof a portionof Figure 1, the modificationspecifically consisting of modifying the manner in which the safe startrelay 42 controls the inter-relationship of Geiger tube 16 and dischargedevice 19. In the modification of Figure 2 the safe start relay 42 isprovided with a pair of normally open switches,

97 and 98, the switch 98 is identical in its function to the switch 44of Figure l. Thecapacitor 71 and recti-z fler 70 again supply a sourceof biasingvoltage for the discharge device 19 and in the modification ofFigure 2 the negative plate of capacitor 71 is connected to the controlelectrode 21 of discharge device 19 through a circuit which includesconductor. 99,: switch 97, conduc: tor 100 and resistor 101. 1

The anode. 18 ofGeiger tube 16 is connected by means i of conductor 102to the anode 20 of dischargedevice 19 and also through resistor 67 tothe upperpositive plate of capacitor 62, as is shown in Figure 1. Thecathode, 17 of Geiger tube 16'is connected directly to the controlelectrode 21 of discharge device 19. Upon.

the safe start relay 42 being energized, cathode 17 of the Geiger tubeis connected to a source of operating voltage on capacitor 62 throughresistor :101, conductor 100, switch 97, conductor 99 and capacitor 71.The connection to the negative plate of capacitor 62 is completed bymeans of conductors 76 and 77 as shown in Figure 2'and by means of thenetwork including resistors 68, 66, 65 and 32 as well as capacitor 31and rectifier 64, as is shown in Figure 1. v

In this modification, with the safe start relay de-energized as shown,the control electrode 21 of discharge device 19 is floating since Geigertube 161is in an unionized condition and in fact operating voltage isnot applied to the Geiger tube. In this condition, discharge device 19becomes conductive, much as'the discharge device 19 of Figure I becameconductive due to the switch 46 of the safe start relay 42 being closed.This checks the flame detector, as above described with regard toFigure 1. Upon flame relay 37 being energized to cause energization ofsafe start relay 42, the switch 97 of Figure 2 is closed and the biasvoltage is then applied to the discharge device 19. An operating voltageis also applied to the Geiger tube 16. The discharge device 19 thereforeceases conduction and the flame relay 37 is de-e'nergized to place theapparatus in the standby condition wherein the flame relay isde-energized, the safe start relay is energized, and operating voltageis applied to the Geiger tube.

Figure 3 shows a further modification of the present invention and hereagain the manner in which the safe start relay 42, the Geiger tube 16and the discharge device 19 are inter-related has been modified.Furthermore, the discharge device 105 is a tetrode and the input circuitto the control electrodes 106 and 107 of this discharge device has alsobeen modified from that shown in Figure 1.

Specifically, the input circuits to the discharge device 105 of Figure 3both involve integration. Considering control electrode 106, thiscontrol electrode is connected to a resistor 108 which is connected inseries with a parallel connected resistor 109 and capacitor 110. Thecontrol electrode 107 is connected to a resistor 111 which is connectedin series with a parallel connected resistor 112 and capacitor 113. Itis advisable in the case of the apparatus of Figure 3 to provideintegration to each of the control electrodes. However, one of thesignals is integrated more than the other. In other words, one of thesignals is delayed or integrated with respect to the other. Thedischarge device 105 is rendered conductive only upon a coincidence ofsignals at the electrodes 106 and 107, in a similar manner to thefunctioning of the discharge device 25 in Figure 1. In this manner theapparatus of Figure 3 discriminates against the background count in theGeiger tube 16 in the same manner as the apparatus of Figure 1.

In the apparatus of Figure 3, resistor 114 is connected in circuit withthe source of direct current voltage including rectifier 61 andcapacitor 62. The voltage developed across this resistor 114 is of thepolarity shown in Figure 3 and when the switch 104 of the safe startrelay 42 is closed, this voltage biases the discharge device 19substantially to cut off. This can be seen by tracing the circuit fromthe cathode 22 of this discharge device through resistor 114, conductor115, switch 104, conductor 116, and resistor 117 to the controlelectrode 21 of discharge device 19. The anode 18 of the Geiger tube 16is connected directly to the anode 20 of discharge device 19, as inFigure 2, and is further connected through the resistor 67 to thepositive plate of the capacitor 62. The cathode 17 of Geiger tube 16 isconnected to the negative terminal of this capacitor 62 through acircuit including resistor 117, conductor 116, switch 104, conductor115, the input circuit of discharge device 105 and capacitor 118 to thelower plate of capacitor 62.

It can be seen that, as was the case in Figures 1 and 2, with the safestart re lay 42 de-energized operating voltage is not applied to theGeiger tube 16 and the presence of flame is simulated. The simulation ofthe presence of flame is accomplished in Figure 3 by breaking the biasconnection from resistor 114 to the control electrode 210i dischargedevice 19. s

Discharge device 19 is then rendered conductive and the current flowingthrough this discharge device develops a signal voltage which isintegrated and applied to' both of the electrodes 106 and 107 of thedischarge device 105, thereby causing flame relay 37 to be energized Ina the manner described in detail in connection with Figure 1, theenergization of flame relay 37 causes the safe start relay 42 to beenergized and this in turn causes the flame relay 37 to becomede-energized. In this manner the operation of the electroniccomponentsof the flame detector are checked, first to insure that the apparatus iscapable of sensing a simulated presence of flame and then to insure thatthe apparatus senses the actual absence of flame at the fuel burnerunit.

The controller 60 is then effective to cause energization of the mainburner control relay 47 to thereby energize the components of the fuelburner unit 10, as previously described in connection with Figure 1.

It can be seen from the above description that I have provided animproved control apparatus having a safe start relay which not onlychecks proper operation of the flame detector but likewisepreventsapplication of operating voltages toa Geiger tube until the quenchingcircuit' is operative thereby providing an improved control apparatuswhich achievesrreliable and safe control of the fuel burner unit 10.Other modifications of the present invention will be apparent to thoseskilled in the artand it is intended that the scope of the presentinvention be limited solely by the scope of the appended claims.

I claim as my invention:

1. Condition sensing apparatus comprising; Geiger tube condition sensingmeans arranged to be subjected to an ionizing" condition, said Geigertube being of the non-selfquenching type; a quenching circuit, circuitmeans connecting said Geiger tube in controlling relation to saidquenching circuitto thereby cause'said quenching circuit to operate andto quench said Geiger tube upon said Geiger tube being subjected to theionizing condition; a

source of voltage, a safe start relay having an actuator and a pair ofnormally open switches; circuit means con trolled by the first switch ofsaid safe start relay in said open position to modify the connection ofsaid Geiger tube to said quenching circuit such that an operatingvoltage is not supplied to said Geiger tube and an ionizing condition issimulated to thereby cause said quenching circuit to be operative,further means controlled by said quenching circuit when operative, meanscontrolled by said last named means arranged to energize said safe startrelay actuator upon said quenching circuit being rendered operative, andcircuitmeans controlled by the second switch of said safe start relayarranged to main tain said safe start relay actuator continuouslyenergized, said first switch of said safe start relay when in energizedposition being arranged to supply an energizing voltage to said Geigertube.

2. A flame detector for use with a fuel burner unit comprising; a Geigertube flame sensor arranged to be positioned to sense the flame at thefuel burner unit, said Geiger .tube' being of the non-selfquenchingtype; a quenching circuit including an electron discharge device,circuit means interconnecting said Geiger tube and said electrondischarge device in mutual control of each other such that ionization ofsaid Geiger tube causes said discharge device to be conductive and saiddischarge device when conductive causes said Geiger tube to be quenched;a normally de-energized safe start relay having an actu ator and a pairof switches, terminals adapted to be con;- nected to a source ofoperating voltage,-circuit means controlled by the first switch of saidsafe start relay arranged to modify the inter-connection of said Geigertube and said quenching circuit toprevent the application of anoperating voltage to said Geiger tube and to cause said discharge deviceto become conductive to thereby simulate the presence of flame upon theinitial application of voltage to said terminals; means controlled bysaid discharge device when conductive, means controlled by saidlast-named means arranged to energize the actuator of said safe startrelay upon said discharge device be coming conductive; circuit meanscontrolled by the second switch of said safe start relay to maintainsaid safe start relay actuator energized, and further circuit meanscontrolled by the first switch of said safe start relay to apply anoperating voltage to said Geiger tube and to cause said discharge deviceto become non-conductive in the absence of flame at thefuel burner unit,said safe start relay thereby functioning to check the ability of saiddischarge device to sense the simulated presence of flame and also toprevent the application of operating voltage to said Geiger tube untilsaid quenching circuit is operative to quench said Geiger tube.

3. Condition sensing apparatus comprising; Gelger tube condition sensingmeans of the non-selfquenching type, a quenching circuit including anelectron discharge device, circuit means interconnecting said Geigertube and said quenching circuit in mutual controlling relationship suchthat upon said Geiger tube experiencing an ionizing condition, saiddischarge device is rendered conductive to subsequently de-ionize saidGeiger tube; a safe start relay having an actuator and switch meanscontrolled thereby; a source of voltage, circuit means interconnectingsaid quenching circuit and said Geiger tube to said source of voltage;said circuit means being controlled by said switch means such that uponthe apparatus bei ng initially connected to-the source of voltage, saidrelay actuator remains de-energized and said Geiger tube is renderedinoperative to sensean ionizing condition and an ionizing condition issimulated to cause energization of said discharge device; meanscontrolled by said discharge device connected in circuit with theactuator of 'said relay to thereby cause energization of said actuatorupon said discharge device responding to the simulated condition, andfurther circuit means controlled by said relay switch means to maintainsaid relay actuator energized once it is energized and render saidGeiger tube operative while removingthesimulated; con dition. t a

4. Control apparatus comprising; Geiger tube condition sensing means ofthe non-selfquenching type, a quenching circuit, means interconnectingsaid Geiger tube and said quenching circuit in mutual controllingrelationship such that upon said Geiger tubebeing subjected to anionizing condition said quenching circuit is rendered effective tosubsequently quench the Geiger tube; a source of voltage, a safe startrelay having an actuator and switch means controlled thereby, circuitmeans controlled by said relay switch means connected in controllingrelationship to said Geiger tube and said quenching circuit to preventthe application of operating voltage to said Geiger tube and to simulatethe ionizing condition and thereby render said quenching circuitefiective so long as the actuator of said safe start relay remainsde-energized; means controlled bysaid quenching circuit when effectivearranged to connect the actuator of said safe start relay to said sourceof voltage to thereby energize said actuator; said relay switch means inenergized condition removing the simulated ionizing condition to therebycause said quenching circuit to become ineffective, and also applyingoperative voltage to said Geiger-tube; a main control relay having anactuator; and energizingcircuit means for the actuator of said maincontrol relay :controlled by said relay switch means in energizedcondition and by said means controlled by said quenching circuit whensaid quenching circuit is ineffective.

5. Burner control apparatus for use with a fuel burner unitcomprising;Geiger tube flame sensing means arranged to beqsubjected toa flame atthe fuel burner unit, said Geiger tube beingofithe non-selfquenchingtype; a quenching circuit, circuit means interconnecting said Geigertube andsaid quenching circuit in mutually controlling relationship suchthat upon said Geiger tube being subjected to a flame, said quenchingcircuit is rendered operative to thereby quench said Geiger tube; a pairof voltage input terminals arranged to be con nected to a source ofoperating voltage, a safe start relay having an actuator and switchmeans controlledthereby, circuit means controlled by theswitch means ofsaid safe start relay connected to said Geiger tube and said quenchingcircuit to disconnect said Geiger tube from said, input terminalsand ,tosimulate the presence of flame so long as the actuator of said safestart relay 'is de-energized, said circuit means thereby causing saidquenching circuit to become operative; means controlled by saidquenching circuit, further circuit means controlled by said last namedmeans and arranged to ener-,

gize the actuator of said safe start relay upon said quenching circuitbecoming operative; circuit means controlled by the switch means of saidsafe start relay to maintain said safe start relay actuator energized,said safe startrelay switch means when said actuator is energizedfunctioning to connect said Geiger tube to 1 said input terminals andthereby apply an operating, voltage to said Geiger tube and to alsoremove the simulation of flame whereby said Geiger tube senses theactual absence of flame at thefuel burner unit and said quenchingcircuit in turn becomes inoperative; a burner control relay having anactuator and switch means controlled thereby, energizing circuit meansfor the actuator of saidburner control relay arranged to, energize theactuator thereof upon said safe start relay actuator being energized andupon said quenching circuit assuming its inoperative condition; andfurther circuit means adapted to be connected to said fuel burner unitand controlled by the switch means of said burner 1 control relay.

6. Burnercontrol apparatus for use with a fuel burner unit comprising; aGeiger tube flame sensor oflthe nonselfquenching type arranged to bepositioned toview the flame at the fuel burner, a quenching circuitincluding an electron discharge device, a source of voltage; circuitmeans interconnecting said Geiger tube, said discharge device and saidsource of voltage so that upon said Gelger tubebeing subjected to aflame said discharge device becomes conductive and said discharge devicein the conducting state functions to quench said Geiger tube; a flamerelay having switch means and an actuator which is connected to becontrolled by said discharge device and to be energized upon saiddischargedevice becoming conductive, a safe start relay having switchmeans and an actuator, circuit means controlled by the switch means ofsaid safe start relay when in a de-energized position arranged to modifysaid first named circuit means to simulate aflarne and to disconnectsaid Geiger tube from said source of voltage to thereby render saidGeiger tube insensitiveto a random ionizing event, said;las t .namedcircuit means thereby rendering said discharge device conductive tocause energization of said flame relay actuator; circuit meanscontrolledby the switch means of saidflame relay arranged to energizethe actu-j said energized position being arranged to apply an oper-Iating voltage to sald Geiger tube and to cease the simu-,

lation of flame to thereby cause said discharge device to becomemoperatlve-and said flame relay actuator to be de-energized; a mainburner control relay having an actuator and switch means controlledthereby, energizing cir-; cult means for the actuator of said mainburner control 13 relay including the switch means of said flame relaywhen de-energized, and the switch means of said safe start relay whenenergized, and further circuit means adapted to be connected to the fuelburner unit and controlled by the switch means of said main burnercontrol relay, the apparatus thereby functioning to check the properoperation of said quenching circuit and to prevent the application of anoperating voltage to said Geiger tube until said quenching circuit isoperative.

7. Condition sensing apparatus comprising; Geiger tube condition sensingmeans of the non-selfquenching type, quenching means including anelectron discharge device having an anode, a cathode and a controlelectrode, a source of operating voltage for said Geiger tube and saiddischarge device, a safe start relay having an actuating winding and afirst normally closed switch and second and third normally open switchescontrolled thereby, circuit means connecting the anode and cathode ofsaid discharge device to said source of operating voltage, biasing meansconnected to said cathode and said control electrode to bias saiddischarge device substantially to cutoff, circuit means controlled bysaid first normally closed switch of said safe start relay connectingsaid control electrode to said anode to thereby render said dischargedevice conductive so long as saidsafe start relay remains tie-energized,means controlled by said discharge device and arranged to energize theactuating winding of said safe start relay upon said discharge devicebecoming conductive, circuit means controlled by the second normallyopen switch of said safe start relay maintaining said safe start relayactuator energized, and further circuit means controlled by the thirdnormally open switch of said safe start relay connecting said Geigertube from the anode to the control electrode of said discharge device,said safe start relay thereby functioning to simulate the presence of acondition and to prevent the application of an operating voltage to saidGeiger tube until said discharge device is in a conducting condition.

8. Condition sensing apparatus. comprising; Geiger tube conditionsensing means of the non-selfquenching type, quenching means includingan electron discharge device having an anode, a cathode, a controlelectrode, circuit means connecting the anode of said Geiger tube to theanode of said discharge device and the cathode of said Geiger tube tothe control electrode of said discharge device, a source of operatingvoltage connected to the anode and cathode of said discharge device,biasing means for said discharge device, a safe start relay having anactuator and first and second normally open switches controlled thereby,circuit means connecting said biasing means from said cathode to saidcontrol electrode in series with the first of said normally openswitches, said first normally open switch when in an open conditionmaintaining said biasing means disconnected from said discharge deviceand maintaining said Geiger tube disconnected from said source ofoperating voltage to thereby cause said discharge device to becomeconductive, means controlled by said discharge device when conductivearranged to energize the actuator of said safe start relay, said safestart relay thereby causing said first and second normally open switchesto close, to apply said biasing potential to said control electrode andto apply said operating voltage to said Geiger tube, and further circuitmeans controlled by the second normally open switch of said safe startrelay arranged to maintain the actuator thereof energized.

9. Condition sensing apparatus comprising; Geiger tube condition sensingmeans of a non-selfquenching type,

14 quenching means including an electron discharge device having ananode, a cathode and a control electrode, circuit means connecting theanode of said Geiger tube to a charge device to the junction of saidfirst and second.

resistors to thereby apply an operating voltage to said dischargedevice, a safe start relay having an actuator and a pair of normallyopen switches, circuit means connecting said control electrode through afirst of said normally open switches to the end therminal of said secondresistor to thereby apply a bias to said discharge device tosubstantially cut oil? said discharge device and to further apply anoperating voltage to said Geiger tube when said first switch is closed,said safe start relay in de-energized position functioning to preventthe application of operating voltage to said Geiger tube and to rendersaid discharge device conductive, means controlled by said dischargedevice when conductive arranged to energize the actuator of said safestart relay, and further means controlled by the second normally openswitch of said safe start relay to maintain the actuator thereofenergized.

10. Burner control apparatus for use with a fuel burner unit comprising;Geiger tube flame sensing means of the non-selfquenching type, quenchingmeans for said Geiger tube, circuit means interconnecting said Geigertube and said quenching means in mutual controlling relationship suchthat ionization of said Geiger tube due to the presence of flamecontrols said quenching means to cause subsequent quenching of saidGeiger tube; a flamerelay having an actuating winding and switch meanscontrolled thereby, circuit means connecting said flame relay winding tobe energized by said quenching means upon said quenching means beingrendered operative to quench said Geiger tube; a safe start relay havingan actuating winding and switch means controlled thereby, circuit meansconnecting said safe start relay switch means in controllingrelationship to said quenching means and said Geiger tube to prevent theapplication of operating voltage to said Geiger tube and to simulate thepresence of flame so long as said safe start relay winding isde-energized, energizing circuit means for the winding of said safestart relay controlled by the switch means of said flame relay toenergize said safe start relay winding upon said flame relay windingbeing energized, holding energizing circuit means for said safe startrelay winding controlled by the switch means of said safe start relay, amain burner control relay including a winding and switch means adaptedto be connected to a fuel burner unit, initial energizing circuit meansfor said main control relay winding controlled by the switch means ofsaid flame relay and the switch means of said state start relay toprovide energization of said control relay winding upon said flame relaywinding being de-energized and upon said safe start relay winding beingenergized, and holding circuit means for said main control relay windingcontrolled by the switch means of said main control relay.

References Cited in the file of this patent UNITED STATES PATENTS

